Detect permutation in matrix
Last updated: August 30, 2025
Quick Overview
Given a 2D matrix and a target permutation, determine if any row or column in the matrix contains a permutation of the target. The function should return true if such a permutation exists, and false otherwise. The input will consist of the matrix and the target permutation as an array of integers.
Grafana Labs
August 30, 20257
11
4,821 solved
Given a 2D matrix and a target permutation, determine if any row or column in the matrix contains a permutation of the target. The function should return true if such a permutation exists, and false otherwise. The input will consist of the matrix and the target permutation as an array of integers.
This coding problem is frequently asked during Take-home Project at Grafana Labs. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Grafana Labs expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you modify your solution to handle streaming input?
- What if the input doesn't fit in memory?
- How would your solution change if the input was sorted?
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Problem Analysis
To detect if any row or column in the matrix contains a permutation of the target, we can utilize the frequency counting method. The underlying pattern here is similar to using a hash map to count occ...
Approach
- Frequency Count of Target: Create a frequency count of the elements in the target permutation using a hash map (or dictionary). For example, for the target [1, 2, 2], the frequency map would be...
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